Foamable polypropylene compositions

ABSTRACT

The present invention relates to a polypropylene composition, an injection molded article comprising the polypropylene composition, a foamed article comprising the polypropylene composition as well as the use of a polypropylene homopolymer (H-PP1) for reducing the 5stiffness reduction factor of a foamed injection molded article by at least 40 as determined by the difference of the flexural modulus measured according to ISO 178 of the non-foamed and foamed injection molded article and compared to an article comprising the same amount of a polypropylene which has been polymerized in the presence of a Ziegler-Natta catalyst.

The present invention relates to a polypropylene composition, aninjection molded article comprising the polypropylene composition, afoamed article comprising the polypropylene composition as well as theuse of a polypropylene homopolymer (H-PP1) for reducing the stiffnessreduction factor of a foamed injection molded article by at least 40 asdetermined by the difference of the flexural modulus measured accordingto ISO 178 of the non-foamed and foamed injection molded article andcompared to an article comprising the same amount of a polypropylenewhich has been polymerized in the presence of a Ziegler-Natta catalyst.

Polypropylene is used in many applications and is for instance thematerial of choice in many fields such as automotive applicationsbecause they can be tailored to specific purposes needed. However, therecent demand in plastic industry is towards weight reduction. Foamingof polymer compounds via injection-molding (FIM) technology gains wideinterest both scientifically and industrially due to its capability toproduce low-density parts with high geometrical accuracy and improveddimensional stability. With this technique, a product with a cellularcore and solid skin can be molded in a single operation. Basically, FIMincludes the use of an inert gas that is to be dispersed in the polymermelt or by pre-blending a resin with a chemical blowing (or foaming)agent which under heat releases inert gas. The gas bubbles then expandwithin the melt, filling the mould and creating the internal cellularstructure. In injection molding of thermoplastics containing a blowingagent the mixture is held under sufficient back pressure to retain thegas and prevent premature expansion. Depending on the weightrequirements, a specific amount of material is dosed and the melt isinjected into the mold. The entrapped gas expands as soon as themelt/gas mixture enters the empty mould unless a sufficiently highenough counter pressure is applied. Achieving uniform andhigh-cell-density microstructure, which is critical for obtainingsuperior mechanical properties and excellent emissions in foamedplastics is challenging in FIM and can be controlled by processconditions. The influence of process conditions such as blowing agentcontent, mould temperature, melt temperature, injection pressure, andback pressure were varied in order to produce high quality foam in termsof low skin thickness, small cell sizes, and narrow cell sizedistribution is well known. However, the influence of polymer design onthe foamed structure and emissions has been rarely investigated so far.

As a result, polypropylene compositions with excellent foamability arestill desired. Furthermore, it is desired that these polypropylenecompositions have a low volatile content and good balance of mechanicalproperties.

The finding of the present invention is that a polypropylene compositionhaving excellent foamability in combination with a low volatile contentand good balance of mechanical properties can be obtained with aspecific polypropylene homopolymer.

Therefore the present invention is directed to a polypropylenecomposition comprising

-   -   a) from 45 to 97.5 wt.-%, based on the total weight of the        composition, of a polypropylene homopolymer (H-PP1) having        -   i) a melting temperature Tm measured by differential            scanning calorimetry (DSC) in the range from 150 to 160° C.,        -   ii) a content of 2,1 erythro regiodefects as determined from            ¹³C-NMR spectroscopy in the range from 0.50 to 1.00 mol.-%,        -   iii) an isotactic triad fraction (mm) determined from            ¹³C-NMR spectroscopy of at least 97.5%, and        -   iv) a xylene cold soluble fraction (XCS) determined at            23° C. according ISO 16152 of equal or below 1.5 wt.-%,    -   b) from 0 to 55 wt.-%, based on the total weight of the        composition, of a polypropylene (PP2),    -   c) from 0 to 30 wt.-%, based on the total weight of the        composition, of a filler (F), and    -   d) from 2.5 to 5 wt.-%, based on the total weight of the        composition, of at least one additive selected from the group        consisting of colorants, pigments such as carbon black,        stabilisers, acid scavengers, nucleating agents, foaming agents,        antioxidants and mixtures thereof,    -   wherein the sum of the amount of the polypropylene homopolymer        (H-PP1), the polypropylene (PP2), the filler (F) and the at        least one additive in the polypropylene composition is 100.0        wt.-%.

According to one embodiment of the present invention, the compositioncomprises, preferably consists of, a) from 95 to 97.5 wt.-%, based onthe total weight of the composition, of the polypropylene homopolymer(H-PP1), and b) from 2.5 to 5 wt.-%, based on the total weight of thecomposition, of at least one additive selected from the group consistingof colorants, pigments such as carbon black, stabilisers, acidscavengers, nucleating agents, foaming agents and mixtures thereof.

According to another embodiment of the present invention, thecomposition comprises, preferably consists of, a) from 45 to 52.5 wt.-%,based on the total weight of the composition, of the polypropylenehomopolymer (H-PP1), b) from 45 to 55 wt.-%, based on the total weightof the composition, of a polypropylene (PP2), and c) from 2.5 to 5wt.-%, based on the total weight of the composition, of at least oneadditive selected from the group consisting of colorants, pigments suchas carbon black, stabilisers, acid scavengers, nucleating agents,foaming agents and mixtures thereof.

According to yet another embodiment of the present invention, thecomposition has a) a melt flow rate MFR₂ (230° C.) measured according toISO 1133 in the range of 15.0 to 80.0 g/10 min; and/or b) a content ofvolatile organic compounds no greater than 170 μg/g composition innon-foamed injection moulded parts; and/or c) a content of volatileorganic compounds no greater than 200 μg/g composition in pellet form;and/or d) a glass transition temperature Tg (measured with DMTAaccording to ISO 6721-7) of 0° C. or above, preferably +1° C. or above.

According to one embodiment of the present invention, the compositioncomprises from 0.1 to 0.5 wt.-%, based on the total weight of thecomposition, of a nucleating agent, preferably a nucleating agentcontaining 1,2-cyclohexane dicarboxylic acid.

According to another embodiment of the present invention, thepolypropylene (PP2) is a polypropylene homopolymer (H-PP2).

According to yet another embodiment of the present invention, thepolypropylene homopolymer (H-PP1) and/or the polypropylene (PP2)has/have a melt flow rate MFR₂ (230° C.) measured according to ISO 1133in the range of 15.0 to 100.0 g/10 min, preferably in the range from25.0 to 90.0 g/10 min.

According to one embodiment of the present invention, the melt flow rateMFR₂ (230° C.) measured according to ISO 1133 of the polypropylenehomopolymer (H-PP1) differs from the melt flow rate MFR₂ (230° C.)measured according to ISO 1133 of the polypropylene (PP2) by less than20.0 g/10 min, preferably less than 15.0 g/10 min and most preferablyless than 10.0 g/min.

According to another embodiment of the present invention, thepolypropylene homopolymer (H-PP1) i) is unimodal, and/or ii) has amolecular weight distribution Mw/Mn measured according to ISO 16014 inthe range of ≤4.0, preferably in the range from 2.0 to 4.0, and morepreferably in the range from 2.5 to 4.0.

According to yet another embodiment of the present invention, thepolypropylene homopolymer (H-PP1) has i) a melting temperature Tmmeasured by differential scanning calorimetry (DSC) in the range from150 to 160° C., ii) a content of 2,1 erythro regiodefects as determinedfrom ¹³C-NMR spectroscopy in the range from 0.50 to 1.00 mol.-%, iii) anisotactic triad fraction (mm) determined from ¹³C-NMR spectroscopy of atleast 97.5%, and iv) a xylene cold soluble fraction (XCS) determined at23° C. according ISO 16152 equal or below 1.5 wt.-%.

According to one embodiment of the present invention, the polypropylene(PP2) has i) a melting temperature Tm measured by differential scanningcalorimetry (DSC) in the range from 162 to 170° C., and/or ii) a contentof 2,1 erythro regiodefects as determined from ¹³C-NMR spectroscopy of≤0.10 mol.-%, and/or iii) an isotactic triad fraction (mm) determinedfrom ¹³C-NMR spectroscopy in the range from 95.0 to 98.0%, and/or iv) amolecular weight distribution Mw/Mn measured according to ISO 16014 inthe range of ≥4.0, and/or v) a xylene cold soluble fraction (XCS)determined at 23° C. according ISO 16152 in the range from 1.5 to 3.5wt.-%.

According to another embodiment of the present invention, thecomposition has a bimodal molecular structure.

According to yet another embodiment of the present invention, the filler(F) is selected from talcum, mica, wollastonite, glass fibers, carbonfibers and mixtures thereof.

According to another aspect of the present invention, an injectionmolded article comprising the polypropylene composition as definedherein is provided.

According to a further aspect of the present invention, a foamedarticle, preferably foamed injection molded article, comprising thepolypropylene composition as defined herein is provided.

According to a still further aspect, the use of a polypropylenehomopolymer (H-PP1) for reducing the stiffness reduction factor of afoamed injection molded article by at least 40 as determined by thedifference of the flexural modulus measured according to ISO 178 of thenon-foamed and foamed injection molded article and compared to anarticle comprising the same amount of a polypropylene which has beenpolymerized in the presence of a Ziegler-Natta catalyst is provided,wherein the polypropylene homopolymer (H-PP1) has i) a meltingtemperature Tm measured by differential scanning calorimetry (DSC) inthe range from 150 to 160° C., ii) a content of 2,1 erythro regiodefectsas determined from ¹³C-NMR spectroscopy in the range from 0.50 to 1.00mol.-%, iii) an isotactic triad fraction (mm) determined from ¹³C-NMRspectroscopy of at least 97.5%, and iv) a xylene cold soluble fraction(XCS) determined at 23° C. according ISO 16152 of equal or below 1.5wt.-%.

In the following the invention is defined in more detail.

The Polypropylene Composition

The polypropylene (PP) composition according to this invention comprises

-   -   a) from 45 to 97.5 wt.-%, based on the total weight of the        composition, of a polypropylene homopolymer (H-PP1) having        -   i) a melting temperature Tm measured by differential            scanning calorimetry (DSC) in the range from 150 to 160° C.,        -   ii) a content of 2,1 erythro regiodefects as determined from            ¹³C-NMR spectroscopy in the range from 0.50 to 1.00 mol.-%,        -   iii) an isotactic triad fraction (mm) determined from            ¹³C-NMR spectroscopy of at least 97.5%, and        -   iv) a xylene cold soluble fraction (XCS) determined at            23° C. according ISO 16152 of equal or below 1.5 wt.-%,    -   b) from 0 to 55 wt.-%, based on the total weight of the        composition, of a polypropylene (PP2),    -   c) from 0 to 30 wt.-%, based on the total weight of the        composition, of a filler (F), and    -   d) from 2.5 to 5 wt.-%, based on the total weight of the        composition, of at least one additive selected from the group        consisting of colorants, pigments such as carbon black,        stabilisers, acid scavengers, nucleating agents, foaming agents,        antioxidants and mixtures thereof,    -   wherein the sum of the amount of the polypropylene homopolymer        (H-PP1), the polypropylene (PP2), the filler (F) and the at        least one additive in the polypropylene composition is 100.0        wt.-%.

In a preferred embodiment, the polypropylene composition according tothis invention does not comprise (a) further polymer(s) different to thepolymer present in the polypropylene (PP) composition, i.e. different tothe polypropylene homopolymer (H-PP1) and the optional polypropylene(PP2). Typically, if an additional polymer is present, such a polymer isa carrier polymer for additives and thus does not contribute to theimproved properties of the claimed polypropylene composition.

Accordingly in one embodiment the polypropylene composition consists ofthe polypropylene homopolymer (H-PP1), the optional polypropylene (PP2),the optional filler (F) and the at least one additive, which mightcontain low amounts of polymeric carrier material. However, thispolymeric carrier material is not more than 2.0 wt.-%, preferably notmore than 1.6 wt.-%, based on the total weight of the polypropylenecomposition, present in said polypropylene composition.

In one embodiment, it is thus preferred that the polypropylenecomposition consists of

-   -   a) from 45 to 97.5 wt.-%, based on the total weight of the        composition, of a polypropylene homopolymer (H-PP1) having        -   i) a melting temperature Tm measured by differential            scanning calorimetry (DSC) in the range from 150 to 160° C.,        -   ii) a content of 2,1 erythro regiodefects as determined from            ¹³C-NMR spectroscopy in the range from 0.50 to 1.00 mol.-%,        -   iii) an isotactic triad fraction (mm) determined from            ¹³C-NMR spectroscopy of at least 97.5%, and        -   iv) a xylene cold soluble fraction (XCS) determined at            23° C. according ISO 16152 of equal or below 1.5 wt.-%,    -   b) from 0 to 55 wt.-%, based on the total weight of the        composition, of a polypropylene (PP2),    -   c) from 0 to 30 wt.-%, based on the total weight of the        composition, of a filler (F), and    -   d) from 2.5 to 5 wt.-%, based on the total weight of the        composition, of at least one additive selected from the group        consisting of colorants, pigments such as carbon black,        stabilisers, acid scavengers, nucleating agents, foaming agents,        antioxidants and mixtures thereof,    -   wherein the sum of the amount of the polypropylene homopolymer        (H-PP1), the polypropylene (PP2), the filler (F) and the at        least one additive in the polypropylene composition is 100.0        wt.-%.

Preferably, the polypropylene composition comprises, more preferablyconsists of,

-   -   a) from 95 to 97.5 wt.-%, based on the total weight of the        composition, of the polypropylene homopolymer (H-PP1), and    -   b) from 2.5 to 5 wt.-%, based on the total weight of the        composition, of at least one additive selected from the group        consisting of colorants, pigments such as carbon black,        stabilisers, acid scavengers, nucleating agents, foaming agents        and mixtures thereof.

In an alternative embodiment, the polypropylene composition comprises,preferably consists of,

-   -   a) from 45 to 52.5 wt.-%, based on the total weight of the        composition, of the polypropylene homopolymer (H-PP1),    -   b) from 45 to 55 wt.-%, based on the total weight of the        composition, of a polypropylene (PP2), and    -   c) from 2.5 to 5 wt.-%, based on the total weight of the        composition, of at least one additive selected from the group        consisting of colorants, pigments such as carbon black,        stabilisers, acid scavengers, nucleating agents, foaming agents        and mixtures thereof.

In another embodiment, the polypropylene composition comprises,preferably consists of,

-   -   a) from 45 to 80.5 wt.-%, based on the total weight of the        composition, of the polypropylene homopolymer (H-PP1),    -   b) from 15 to 30 wt.-%, based on the total weight of the        composition, of a polypropylene (PP2),    -   c) from 2 to 20 wt.-%, based on the total weight of the        composition, of a filler (F), and    -   d) from 2.5 to 5 wt.-%, based on the total weight of the        composition, of at least one additive selected from the group        consisting of colorants, pigments such as carbon black,        stabilisers, acid scavengers, nucleating agents, foaming agents        and mixtures thereof.

Preferably the polypropylene composition has a melt flow rate MFR₂ (230°C., 2.16 kg) measured according to ISO 1133 in the range from 15.0 to80.0 g/10 min, more preferably in the range from 25.0 to 80 g/10 min,like in the range from 40.0 to 74.0 g/10 min.

Additionally or alternatively, the polypropylene composition has acontent of volatile organic compounds no greater than 200 μg/gcomposition in pellet form, preferably no greater than 180 μg/gcomposition in pellet form and most preferably no greater than 165 μg/gcomposition in pellet form.

Additionally or alternatively, the polypropylene composition has acontent of volatile organic compounds no greater than 170 μg/gcomposition in non-foamed injection moulded parts, preferably no greaterthan 120 μg/g composition in non-foamed injection moulded parts and mostpreferably no greater than 90 μg/g composition in non-foamed injectionmoulded parts.

Additionally or alternatively, the polypropylene composition has a glasstransition temperature Tg (measured with DMTA according to ISO 6721-7)of 0° C. or above, preferably +1° C. or above and most preferably in therange from +1 to +10° C.

In a preferred embodiment, the polypropylene composition has

-   -   a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according        to ISO 1133 in the range from 15.0 to 80.0 g/10 min, more        preferably in the range from 25.0 to 80 g/10 min, like in the        range from 40.0 to 74.0 g/10 min, and/or    -   b) a content of volatile organic compounds no greater than 170        μg/g composition in non-foamed injection moulded parts,        preferably no greater than 120 μg/g composition in non-foamed        injection moulded parts and most preferably no greater than 90        μg/g composition in non-foamed injection moulded parts, and/or    -   c) a content of volatile organic compounds no greater than 200        μg/g composition in pellet form, preferably no greater than 180        μg/g composition in pellet form and most preferably no greater        than 165 μg/g composition in pellet form, and/or    -   d) a glass transition temperature Tg (measured with DMTA        according to ISO 6721-7) of 0° C. or above, preferably +1° C. or        above and most preferably in the range from +1 to +10° C.

For example, the polypropylene (PP) composition has

-   -   a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according        to ISO 1133 in the range from 15.0 to 80.0 g/10 min, more        preferably in the range from 25.0 to 80 g/10 min, like in the        range from 40.0 to 74.0 g/10 min, or    -   b) a content of volatile organic compounds no greater than 170        μg/g composition in non-foamed injection moulded parts,        preferably no greater than 120 μg/g composition in non-foamed        injection moulded parts and most preferably no greater than 90        μg/g composition in non-foamed injection moulded parts, or    -   c) a content of volatile organic compounds no greater than 200        μg/g composition in pellet form, preferably no greater than 180        μg/g composition in pellet form and most preferably no greater        than 165 μg/g composition in pellet form, or    -   d) a glass transition temperature Tg (measured with DMTA        according to ISO 6721-7) of 0° C. or above, preferably +1° C. or        above and most preferably in the range from +1 to +10° C.

For example, the polypropylene (PP) composition has

-   -   a) a melt flow rate MFR₂ (230° C., 2.16 kg) measured according        to ISO 1133 in the range from 15.0 to 80.0 g/10 min, more        preferably in the range from 25.0 to 80 g/10 min, like in the        range from 40.0 to 74.0 g/10 min, and    -   b) a content of volatile organic compounds no greater than 170        μg/g composition in non-foamed injection moulded parts,        preferably no greater than 120 μg/g composition in non-foamed        injection moulded parts and most preferably no greater than 90        μg/g composition in non-foamed injection moulded parts, and    -   c) a content of volatile organic compounds no greater than 200        μg/g composition in pellet form, preferably no greater than 180        μg/g composition in pellet form and most preferably no greater        than 165 μg/g composition in pellet form, and    -   d) a glass transition temperature Tg (measured with DMTA        according to ISO 6721-7) of 0° C. or above, preferably +1° C. or        above and most preferably in the range from +1 to +10° C.

It is preferred that the polypropylene composition can be unimodal ormultimodal, like bimodal. However, it is preferred that thepolypropylene composition has a bimodal molecular structure.

It is appreciated that the polypropylene composition imparts anadvantageous stiffness reduction factor to foamed injection moldedarticles. Thus, it is preferred that the stiffness reduction factor of afoamed injection molded article is reduced by at least 40 as determinedby the difference of the flexural modulus measured according to ISO 178of the non-foamed and foamed injection molded article and compared to anarticle comprising the same amount of a polypropylene which has beenpolymerized in the presence of a Ziegler-Natta catalyst.

The polypropylene composition according to the invention may becompounded and pelletized using any of the variety of compounding andblending machines and methods well known and commonly used in the resincompounding art.

For blending the individual components of the instant polypropylenecomposition a conventional compounding or blending apparatus, e.g. aBanbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin screwextruder may be used. The polypropylene compositions recovered from theextruder/mixer are usually in the form of pellets. These pellets arethen preferably further processed, e.g. by injection molding to generatearticles and products of the inventive composition.

In the following, the individual components of the polypropylenecomposition are described in more detail.

The Polypropylene Homopolymer (H-PP1)

The polypropylene composition must comprise a polypropylene homopolymer(H-PP1) in amounts from 45 to 97.5 wt.-%, based on the total weight ofthe polypropylene composition. Preferably, the polypropylene compositioncomprises the polypropylene homopolymer (H-PP1) in amounts from 80 to97.5 wt.-%, like in the range of 95 to 97.5 wt.-%, based on the totalweight of the polypropylene composition.

It is preferred that the polypropylene homopolymer (H-PP1) has a meltflow rate MFR₂ (230° C., 2.16 kg) measured according to ISO 1133 in therange from 15.0 to 100.0 g/10 min, more preferably in the range from25.0 to 90.0 g/10 min.

The polypropylene homopolymer (H-PP1) can be unimodal or multimodal,like bimodal. However, it is preferred that polypropylene homopolymer(H-PP1) is unimodal.

The expressions “unimodal”, “bimodal” and “multimodal” as used hereinrefer to the modality of the polymer, i.e. the form of its molecularweight distribution curve, which is the graph of the molecular weightfraction as a function of its molecular weight.

When the polypropylene homopolymer (H-PP1) is unimodal with respect tothe molecular weight distribution, it may be prepared in a single stageprocess e.g. as slurry or gas phase process in a slurry or gas phasereactor. Preferably, the unimodal polypropylene homopolymer (H-PP1) ispolymerized in a slurry polymerization. Alternatively, the unimodalpolypropylene homopolymer (H-PP1) may be produced in a multistageprocess using at each stage process conditions which result in similarpolymer properties.

The term “polypropylene homopolymer (H-PP1)” used in the presentinvention relates to a polypropylene that consists substantially, i.e.of more than 98.0 wt.-% of, preferably of more than 99.0 wt.-%, evenmore preferably of more than 99.5 wt.-%, still more preferably of atleast 99.8 wt.-%, of propylene units. In a preferred embodiment, onlypropylene units in the polypropylene homopolymer (H-PP1) are detectable.

It is appreciated that the polypropylene homopolymer (H-PP1) has axylene cold soluble (XCS) content of equal or below 1.5 wt.-%, based onthe total weight of the polypropylene homopolymer (H-PP1). For example,the polypropylene homopolymer (H-PP1) has a xylene cold soluble (XCS)content in the range from 0.1 to 1.5 wt.-%, preferably in the range from0.1 to 1.4 wt.-%, based on the total weight of the polypropylenehomopolymer (H-PP1).

It is a further requirement of the present invention that thepolypropylene homopolymer (H-PP1) has a relatively high meltingtemperature T_(m). More precisely, it is required that the polypropylenehomopolymer (H-PP1) has a melting temperature T_(m) measured bydifferential scanning calorimetry (DSC) in the range from 150 to 160° C.For example, the polypropylene homopolymer (H-PP1) has a meltingtemperature T_(m) measured by differential scanning calorimetry (DSC) inthe range from 152 to 158° C., preferably in the range from 152 to 156°C.

The relatively high melting temperature T_(m) indicates that thepolypropylene homopolymer (H-PP1) has a rather low content ofregiodefects. It is preferred that the polypropylene homopolymer (H-PP1)has a content of 2,1 erythro regiodefects as determined from ¹³C-NMRspectroscopy in the range from 0.50 to 1.00 mol.-%. More preferably, thepolypropylene homopolymer (H-PP1) has 2,1 erythro regiodefects in therange from 0.55 to 0.80 mol.-% and most preferably in the range from0.60 to 0.80 mol.-%, determined by ¹³C-NMR spectroscopy.

Additionally or alternatively, the polypropylene homopolymer (H-PP1) hasan isotactic triad fraction (mm) determined from ¹³C-NMR spectroscopy ofat least 97.5%. For example, the polypropylene homopolymer (H-PP1) hasan isotactic triad fraction (mm) determined from ¹³C-NMR spectroscopy ofat least 98.5%, more preferably of at least 99.0%, like in the rangefrom 99.0 to 99.5%.

It is thus one requirement that the polypropylene homopolymer (H-PP1)has

-   -   i) a melting temperature Tm measured by differential scanning        calorimetry (DSC) in the range from 150 to 160° C., preferably        in the range from 152 to 158° C., and most preferably in the        range from 152 to 156° C.,    -   ii) a content of 2,1 erythro regiodefects as determined from        ¹³C-NMR spectroscopy in the range from 0.50 to 1.00 mol.-%,        preferably in the range from 0.55 to 0.80 mol.-% and most        preferably in the range from 0.60 to 0.80 mol.-%,    -   iii) an isotactic triad fraction (mm) determined from ¹³C-NMR        spectroscopy of at least 97.5%, preferably of at least 98.5%,        more preferably of at least 99.0%, like in the range from 99.0        to 99.5%, and    -   iv) a xylene cold soluble fraction (XCS) determined at 23° C.        according ISO 16152 of equal or below 1.5 wt.-%, preferably in        the range from 0.1 to 1.5 wt.-%, and most preferably in the        range from 0.1 to 1.4 wt.-%.

It is preferred that the polypropylene homopolymer (H-PP1) has a weightaverage molecular weight (Mw) in the range from 80 to 500 kg/mol,preferably in the range from 100 to 400 kg/mol, more preferably in therange from 120 to 350 k/mol, and/or a number average molecular weight(Mn) of 20 to 200 kg/mol, more preferably 50 to 150 kg/mol, determinedby GPC according to ISO 16014.

It is preferred that the polypropylene homopolymer (H-PP1) has amolecular weight distribution Mw/Mn measured according to ISO 16014 of≤4.0, preferably in the range from 1.5 to 4.0, more preferably in therange from 2.0 to 4.0, and most preferably in the range from 2.5 to 4.0.

Thus, in one embodiment the polypropylene homopolymer (H-PP1)

-   -   i) is unimodal, and/or    -   ii) has a molecular weight distribution Mw/Mn measured according        to ISO 16014 in the range of ≤4.0, preferably in the range from        2.0 to 4.0, and more preferably in the range from 2.5 to 4.0.

For example, the polypropylene homopolymer (H-PP1)

-   -   i) is unimodal, or    -   ii) has a molecular weight distribution Mw/Mn measured according        to ISO 16014 in the range of ≤4.0, preferably in the range from        2.0 to 4.0, and more preferably in the range from 2.5 to 4.0.

Alternatively, the polypropylene homopolymer (H-PP1) has

-   -   i) is unimodal, and    -   ii) has a molecular weight distribution Mw/Mn measured according        to ISO 16014 in the range of ≤4.0, preferably in the range from        2.0 to 4.0, and more preferably in the range from 2.5 to 4.0.

The polypropylene homopolymer (H-PP1) is preferably produced by asingle- or multistage process polymerization of propylene such as bulkpolymerization, gas phase polymerization, slurry polymerization,solution polymerization or combinations thereof. The polypropylenehomopolymer (H-PP1) can be made either in loop reactors or in acombination of loop and gas phase reactor. Those processes are wellknown to one skilled in the art.

In order to overcome the drawbacks of the prior art, it is appreciatedthat the polypropylene homopolymer (H-PP1) must be polymerized in thepresence of a single-site catalyst.

It is preferred that the catalyst system includes a catalyst componentaccording to formula (I)

wherein

M is zirconium or hafnium;

each X independently is a sigma-donor ligand

L is a bridge of formula -(ER¹⁰ ₂)_(y)—;

y is 1 or 2;

E is C or Si;

each R¹⁰ is independently a C₁-C₂₀-hydrocarbyl group, tri(C₁-C₂₀alkyl)silyl group, C₆-C₂₀ aryl group, C₇-C₂₀ arylalkyl group or C₇-C₂₀alkylaryl group or L is an alkylene group such as methylene or ethylene;

R¹ are each independently the same or are different from each other andare a CH₂—R¹¹ group, with R¹¹ being H or linear or branched C₁-C₆ alkylgroup, C₃-C₈ cycloalkyl group, C₆-C₁₀ aryl group;

R³, R⁴ and R⁵ are each independently the same or different from eachother and are H or a linear or branched C₁-C₆ alkyl group, C₇-C₂₀arylalkyl group, C₇-C₂₀ alkylaryl group, or C₆-C₂₀ aryl group with theproviso that if there are four or more R³, R⁴ and R⁵ groups differentfrom H present in total, one or more of R³, R⁴ and R⁵ is other than tertbutyl;

R⁷ and R⁸ are each independently the same or different from each otherand are H, a CH₂—R¹² group, with R¹² being H or linear or branched C₁-C₆alkyl group, SiR¹³ ₃, GeR¹³ ₃, OR¹³, SR¹³, NR¹³ ₂,

wherein

R¹³ is a linear or branched C₁-C₆ alkyl group, C₇-C₂₀ alkylaryl groupand C₇-C₂₀ arylalkyl group or C₆-C₂₀ aryl group.

The catalyst system may include also

-   (ii) a cocatalyst system comprising a boron containing cocatalyst    and an aluminoxane cocatalyst;

It should be stressed that, in some instances the use of such cocatalystmay not be required. The catalyst system of the invention can be used innon-supported form or in solid form. The catalyst system of theinvention may be used as a homogeneous catalyst system or heterogeneouscatalyst system.

The catalyst system of the invention in solid form, preferably in solidparticulate form can be either supported on an external carriermaterial, like silica or alumina, or, in a particularly preferredembodiment, is free from an external carrier, however still being insolid form. For example, the solid catalyst system is obtainable by aprocess in which

(a) a liquid/liquid emulsion system is formed, said liquid/liquidemulsion system comprising a solution of the catalyst components (i) and(ii) dispersed in a solvent so as to form dispersed droplets; and

(b) solid particles are formed by solidifying said dispersed droplets.

Particular complexes of the invention include:

Rac-anti-dimethylsilanediyl[2-methyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Rac-anti-dimethylsilanediyl[2-iso-butyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Rac-anti-dimethylsilanediyl[2-neo-pentyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Rac-anti-dimethylsilanediyl[2-benzyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Rac-anti-dimethylsilanediyl[2-cyclohexylmethyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Race-anti-dimethylsilanediyl[2-methyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Rac-anti-dimethylsilanediyl[2-iso-butyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Rac-anti-dimethylsilanediyl[2-neo-pentyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl,

Rac-anti-dimethylsilanediyl[2-benzyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl, and

Rac-anti-dimethylsilanediyl[2-cyclohexylmethyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenylzirconium dichloride or dimethyl.

The catalysts have been described inter alia in WO2015/011135 which isincorporated by reference herewith. A particularly preferred catalyst iscatalyst number 3 of WO2015/011135. The preparation of the metalloceneshas been described in WO2013/007650 which is incorporated by referenceherewith. The complex preparation of the particular preferred catalysthas been described as E2 in WO2013/007650.

For the avoidance of doubt, any narrower definition of a substituentoffered above can be combined with any other broad or narroweddefinition of any other substituent.

Throughout the disclosure above, where a narrower definition of asubstituent is presented, that narrower definition is deemed disclosedin conjunction with all broader and narrower definitions of othersubstituents in the application.

The ligands required to form the complexes and hence catalysts/catalystsystem of the invention can be synthesised by any process and theskilled organic chemist would be able to devise various syntheticprotocols for the manufacture of the necessary ligand materials. ForExample WO2007/116034 discloses the necessary chemistry. Syntheticprotocols can also generally be found in WO2002/02576, WO2011/135004,WO2012/084961, WO2012/001052, WO2011/076780 and WO2015/158790. Theexamples section also provides the skilled person with sufficientdirection.

As stated above a cocatalyst is not always required. However, when used,the cocatalyst system comprises a boron containing cocatalyst as well asan aluminoxane cocatalyst.

The aluminoxane cocatalyst can be one of formula (II):

where n is usually from 6 to 20 and R has the meaning below.

Aluminoxanes are formed on partial hydrolysis of organoaluminumcompounds, for example those of the formula AlR₃, AlR₂Y and Al₂R₃Y₃where R can be, for example, C₁-C₁₀ alkyl, preferably C₁-C₅ alkyl, orC₃-C₁₀-cycloalkyl, C₇-C₁₂-arylalkyl or alkylaryl and/or phenyl ornaphthyl, and where Y can be hydrogen, halogen, preferably chlorine orbromine, or C₁-C₁₀ alkoxy, preferably methoxy or ethoxy. The resultingoxygen-containing aluminoxanes are not in general pure compounds butmixtures of oligomers of the formula (II).

The preferred aluminoxane is methylaluminoxane (MAO). Since thealuminoxanes used according to the invention as cocatalysts are not,owing to their mode of preparation, pure compounds, the molarity ofaluminoxane solutions hereinafter is based on their aluminium content.

According to the present invention the aluminoxane cocatalyst is used incombination with a boron containing cocatalyst, i.e. when a cocatalystsystem or a cocatalyst is present, which is usually not required.

Boron based cocatalysts of interest include those of formula (III)BY₃  (III)

wherein Y independently is the same or can be different and is ahydrogen atom, an alkyl group of from 1 to about 20 carbon atoms, anaryl group of from 6 to about 15 carbon atoms, alkylaryl, arylalkyl,haloalkyl or haloaryl each having from 1 to 10 carbon atoms in the alkylradical and from 6-20 carbon atoms in the aryl radical or fluorine,chlorine, bromine or iodine. Preferred examples for Y are methyl,propyl, isopropyl, isobutyl or trifluoromethyl, unsaturated groups suchas aryl or haloaryl like phenyl, tolyl, benzyl groups, p-fluorophenyl,3,5-difluorophenyl, pentachlorophenyl, pentafluorophenyl,3,4,5-trifluorophenyl and 3,5-di(trifluoromethyl)phenyl. Preferredoptions are trifluoroborane, triphenylborane,tris(4-fluorophenyl)borane, tris(3,5-difluorophenyl)borane,tris(4-fluoromethylphenyl)borane, tris(2,4,6-trifluorophenyl)borane,tris(penta-fluorophenyl)borane, tris(tolyl)borane,tris(3,5-dimethyl-phenyl)borane, tris(3,5-difluorophenyl)borane and/ortris (3,4,5-trifluorophenyl)borane.

Particular preference is given to tris(pentafluorophenyl)borane.

Borates can be used, i.e. compounds containing a borate 3+ ion. Suchionic cocatalysts preferably contain a non-coordinating anion such astetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitablecounterions are protonated amine or aniline derivatives such asmethylammonium, anilinium, dimethylammonium, diethylammonium,N-methylanilinium, diphenylammonium, N,N-dimethylanilinium,trimethylammonium, triethylammonium, tri-n-butylammonium,methyldiphenylammonium, pyridinium, p-bromo-N,N-dimethylanilinium orp-nitro-N,N-dimethylanilinium.

Preferred ionic compounds which can be used according to the presentinvention include:

triethylammoniumtetra(phenyl)borate,

tributylammoniumtetra(phenyl)borate,

trimethylammoniumtetra(tolyl)borate,

tributylammoniumtetra(tolyl)borate,

tributylammoniumtetra(pentafluorophenyl)borate,

tripropylammoniumtetra(dimethylphenyl)borate,

tributylammoniumtetra(trifluoromethylphenyl)borate,

tributylammoniumtetra(4-fluorophenyl)borate,

N,N-dimethylcyclohexylammoniumtetrakis(pentafluorophenyl)borate,

N,N-dimethylbenzylammoniumtetrakis(pentafluorophenyl)borate,

N,N-dimethylaniliniumtetra(phenyl)borate,

N,N-diethylaniliniumtetra(phenyl)borate,

N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate,

N,N-di(propyl)ammoniumtetrakis(pentafluorophenyl)borate,

di(cyclohexyl)ammoniumtetrakist(pentafluorophenyl)borate,

triphenylphosphoniumtetrakis(phenyl)borate,

triethylphosphoniumtetrakis(phenyl)borate,

diphenylphosphoniumtetrakis(phenyl)borate,

tri(methylphenyl)phosphoniumtetrakis(phenyl)borate,

tri(dimethylphenyl)phosphoniumtetrakis(phenyl)borate,

triphenylcarbeniumtetrakis(pentafluorophenyl)borate,

or ferroceniumtetrakis(pentafluorophenyl)borate.

Preference is given to triphenylcarbeniumtetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammoniumtetrakis(pentafluorophenyl)borateor N,N-dimethylbenzylammoniumtetrakis(pentafluorophenyl)borate.

Suitable amounts of cocatalyst will be well known to the skilled man.

The molar ratio of boron to the metal ion of the metallocene may be inthe range 0.5:1 to 10:1 mol/mol, preferably 1:1 to 10:1, especially 1:1to 5:1 mol/mol.

The molar ratio of Al in the aluminoxane to the metal ion of themetallocene may be in the range 1:1 to 2000:1 mol/mol, preferably 10:1to 1000:1, and more preferably 50:1 to 500:1 mol/mol.

The catalyst of the invention can be used in supported or unsupportedform. The particulate support material used is preferably an organic orinorganic material, such as silica, alumina or zirconia or a mixed oxidesuch as silica-alumina, in particular silica, alumina or silica-alumina.The use of a silica support is preferred. The skilled man is aware ofthe procedures required to support a metallocene catalyst.

Especially preferably the support is a porous material so that thecomplex may be loaded into the pores of the support, e.g. using aprocess analogous to those described in WO94/14856 (Mobil), WO95/12622(Borealis) and WO2006/097497. The particle size is not critical but ispreferably in the range 5 to 200 μm, more preferably 20 to 80 μm. Theuse of these supports is routine in the art.

In an alternative embodiment, no support is used at all. Such a catalystsystem can be prepared in solution, for example in an aromatic solventlike toluene, by contacting the metallocene (as a solid or as asolution) with the cocatalyst, for example methylaluminoxane previouslydissolved in an aromatic solvent, or can be prepared by sequentiallyadding the dissolved catalyst components to the polymerization medium.

In one particularly preferred embodiment, no external carrier is usedbut the catalyst is still presented in solid particulate form. Thus, noexternal support material, such as inert organic or inorganic carrier,for example silica as described above is employed.

In order to provide the catalyst of the invention in solid form butwithout using an external carrier, it is preferred if a liquid/liquidemulsion system is used. The process involves forming dispersingcatalyst components (i) and (ii) in a solvent, and solidifying saiddispersed droplets to form solid particles.

In particular, the method involves preparing a solution of one or morecatalyst components; dispersing said solution in an solvent to form anemulsion in which said one or more catalyst components are present inthe droplets of the dispersed phase; immobilising the catalystcomponents in the dispersed droplets, in the absence of an externalparticulate porous support, to form solid particles comprising the saidcatalyst, and optionally recovering said particles.

This process enables the manufacture of active catalyst particles withimproved morphology, e.g. with a predetermined spherical shape, surfaceproperties and particle size and without using any added external poroussupport material, such as an inorganic oxide, e.g. silica. By the term“preparing a solution of one or more catalyst components” is meant thatthe catalyst forming compounds may be combined in one solution which isdispersed to the immiscible solvent, or, alternatively, at least twoseparate catalyst solutions for each part of the catalyst formingcompounds may be prepared, which are then dispersed successively to thesolvent. In a preferred method for forming the catalyst at least twoseparate solutions for each or part of said catalyst may be prepared,which are then dispersed successively to the immiscible solvent.

More preferably, a solution of the complex comprising the transitionmetal compound and the cocatalyst is combined with the solvent to forman emulsion wherein that inert solvent forms the continuous liquid phaseand the solution comprising the catalyst components forms the dispersedphase (discontinuous phase) in the form of dispersed droplets. Thedroplets are then solidified to form solid catalyst particles, and thesolid particles are separated from the liquid and optionally washedand/or dried. The solvent forming the continuous phase may be immiscibleto the catalyst solution at least at the conditions (e. g. temperatures)used during the dispersing step.

The term “immiscible with the catalyst solution” means that the solvent(continuous phase) is fully immiscible or partly immiscible i.e. notfully miscible with the dispersed phase solution.

Preferably, said solvent is inert in relation to the compounds of thecatalyst system to be produced. Full disclosure of the necessary processcan be found in WO03/051934.

The inert solvent must be chemically inert at least at the conditions(e.g. temperature) used during the dispersing step. Preferably, thesolvent of said continuous phase does not contain dissolved therein anysignificant amounts of catalyst forming compounds. Thus, the solidparticles of the catalyst are formed in the droplets from the compoundswhich originate from the dispersed phase (i.e. are provided to theemulsion in a solution dispersed into the continuous phase).

The terms “immobilisation” and “solidification” are used hereininterchangeably for the same purpose, i.e. for forming free flowingsolid catalyst particles in the absence of an external porousparticulate carrier, such as silica. The solidification happens thuswithin the droplets. Said step can be effected in various ways asdisclosed in said WO03/051934. Preferably solidification is caused by anexternal stimulus to the emulsion system such as a temperature change tocause the solidification. Thus in said step the catalyst component(s)remain “fixed” within the formed solid particles. It is also possiblethat one or more of the catalyst components may take part in thesolidification/immobilisation reaction.

Accordingly, solid, compositionally uniform particles having apredetermined particle size range can be obtained.

Furthermore, the particle size of the catalyst particles of theinvention can be controlled by the size of the droplets in the solution,and spherical particles with a uniform particle size distribution can beobtained.

The process is also industrially advantageous, since it enables thepreparation of the solid particles to be carried out as a one-potprocedure. Continuous or semicontinuous processes are also possible forproducing the catalyst.

In the polymerization process according to the present invention freshcatalyst is preferably only introduced into the first reactor or, ifpresent, into the prepolymerization reactor or vessel, i.e. no freshcatalyst is introduced into the second reactor or any further reactorbeing present upstream of the first reactor or upstream of theprepolymerization vessel. Fresh catalyst denotes the virgin catalystspecies or the virgin catalyst species subjected to a prepolymerization.

The Polypropylene (PP2)

The polypropylene composition may comprise a polypropylene (PP2) inamounts ranging from 0 to 55 wt.-%, based on the total weight of thepolypropylene composition.

In one embodiment, the polypropylene homopolymer (H-PP1) is the onlypolymeric component in the polypropylene composition. That is to say,the polypropylene composition is free of the polypropylene (PP2).

In an alternative embodiment, the polypropylene composition comprisesthe polypropylene (PP2). In this case, it is preferred that thepolypropylene composition has a bimodal molecular structure.

If present, the polypropylene composition comprises the polypropylene(PP2) preferably in amounts from 30 to 55 wt.-%, like in the range of 45to 55 wt.-%, based on the total weight of the polypropylene composition.

In the present invention, the term “polypropylene (PP2)” encompassespolypropylene homopolymers and/or polypropylene copolymers.

Moreover, the term “propylene copolymer” encompasses polypropylenerandom copolymers, heterophasic polymers and mixtures thereof.

As known for the skilled person, random polypropylene copolymer isdifferent from heterophasic polypropylene which is a propylene copolymercomprising a propylene homo or random copolymer matrix component (1) andan elastomeric copolymer component (2) of propylene with one or more ofethylene and C₄-C₈ alpha-olefin copolymers, wherein the elastomeric(amorphous) copolymer component (2) is dispersed in said propylene homoor random copolymer matrix polymer (1).

In one embodiment of the present invention, the polypropylene (PP2)being present in the polypropylene composition is a polypropylenehomopolymer (H-PP2) and/or a polypropylene copolymer (C-PP2). Forexample, the polypropylene composition comprises a polypropylenehomopolymer (H-PP2) or a polypropylene copolymer (C-PP2).

In one specific embodiment, the polypropylene composition comprises apolypropylene homopolymer (H-PP2) as the polypropylene (PP2).

The term “polypropylene homopolymer (H-PP2)” used in the presentinvention relates to a polypropylene that consists substantially, i.e.of more than 98.0 wt.-% of, preferably of more than 99.0 wt.-%, evenmore preferably of more than 99.5 wt.-%, still more preferably of atleast 99.8 wt.-%, of propylene units. In a preferred embodiment, onlypropylene units in the polypropylene homopolymer (H-PP2) are detectable.

It is preferred that the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has a melt flow rate MFR₂ (230° C.,2.16 kg) measured according to ISO 1133 in the range from 15.0 to 100.0g/10 min, more preferably in the range from 25.0 to 90.0 g/10 min.

It is appreciated that the melt flow rate MFR₂ (230° C.) measuredaccording to ISO 1133 of the polypropylene homopolymer (H-PP1) differsfrom the melt flow rate MFR₂ (230° C.) measured according to ISO 1133 ofthe polypropylene (PP2), preferably the polypropylene homopolymer(H-PP2), by less than 20.0 g/10 min, preferably less than 15.0 g/10 minand most preferably less than 10.0 g/min. For example, the melt flowrate MFR₂ (230° C.) measured according to ISO 1133 of the polypropylenehomopolymer (H-PP1) differs from the melt flow rate MFR₂ (230° C.)measured according to ISO 1133 of the polypropylene (PP2), preferablythe polypropylene homopolymer (H-PP2), by 1.0 to 10.0 g/min.

The polypropylene (PP2), preferably the polypropylene homopolymer(H-PP2), can be unimodal or multimodal, like bimodal. However, it ispreferred that polypropylene (PP2), preferably the polypropylenehomopolymer (H-PP2), is unimodal.

The expression “unimodal”, “bimodal” and “multimodal” as used hereinrefers to the modality of the polymer, i.e. the form of its molecularweight distribution curve, which is the graph of the molecular weightfraction as a function of its molecular weight.

It is appreciated that the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has a xylene cold soluble (XCS)content in the range from 1.5 to 3.5 wt.-%, preferably in the range from1.5 to 3.0 wt.-%, based on the total weight of the polypropylene (PP2),preferably the polypropylene homopolymer (H-PP2).

It is further preferred that the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has a relatively high meltingtemperature T_(m). More precisely, it is preferred that thepolypropylene (PP2), preferably the polypropylene homopolymer (H-PP2),has a melting temperature T_(m) that is above the melting temperature ofthe polypropylene homopolymer (H-PP1). For example, the polypropylene(PP2), preferably the polypropylene homopolymer (H-PP2), has a meltingtemperature T_(m) measured by differential scanning calorimetry (DSC) inthe range from 162 to 170° C., preferably in the range from 162 to 168°C.

The relatively high melting temperature T_(m) indicates that thepolypropylene (PP2), preferably the polypropylene homopolymer (H-PP2),has a rather low content of regiodefects. It is preferred that thepolypropylene (PP2), preferably the polypropylene homopolymer (H-PP2),has a content of 2,1 erythro regiodefects as determined from ¹³C-NMRspectroscopy of ≤0.10 mol.-%, preferably of 0.0 mol.-%. As well-known inthe art, polypropylenes having such an amount of 2,1-erythroregiodefects are preferably produced with a Ziegler-Natta catalyst.Accordingly, the polypropylene (PP2), preferably the polypropylenehomopolymer (H-PP2), is preferably produced with a Ziegler-Nattacatalyst.

Additionally or alternatively, the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has an isotactic triad fraction (mm)determined from ¹³C-NMR spectroscopy in the range from 95.0 to 98.0%.

It is preferred that the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has a weight average molecular weight(Mw) in the range from 80 to 500 kg/mol, preferably in the range from100 to 400 kg/mol, more preferably in the range from 120 to 350 k/mol,and/or a number average molecular weight (Mn) of 20 to 200 kg/mol, morepreferably 50 to 150 kg/mol, determined by GPC according to ISO 16014.

It is preferred that the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has a molecular weight distributionMw/Mn measured according to ISO 16014 of ≥4.0, preferably in the rangefrom 4.0 to 8.0, and most preferably in the range from 4.0 to 7.0.

Additionally or alternatively, the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has a density in the range from 0.900to 0.910 g/cm³.

Thus, in one embodiment the polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), has

-   -   i) a melting temperature Tm measured by differential scanning        calorimetry (DSC) in the range from 162 to 170° C., preferably        in the range from 162 to 168° C., and/or    -   ii) a content of 2,1 erythro regiodefects as determined from        ¹³C-NMR spectroscopy of ≤0.10 mol.-%, and/or    -   iii) an isotactic triad fraction (mm) determined from ¹³C-NMR        spectroscopy in the range from 95.0 to 98.0%, and/or    -   iv) a molecular weight distribution Mw/Mn measured according to        ISO 16014 in the range of ≥4.0, preferably in the range from 4.0        to 8.0, and most preferably in the range from 4.0 to 7.0, and/or    -   v) a xylene cold soluble fraction (XCS) determined at 23° C.        according ISO 16152 in the range from 1.5 to 3.5 wt.-%,        preferably in the range from 1.5 to 3.0 wt.-%.

For example, the polypropylene (PP2), preferably the polypropylenehomopolymer (H-PP2), has

-   -   i) a melting temperature Tm measured by differential scanning        calorimetry (DSC) in the range from 162 to 170° C., preferably        in the range from 162 to 168° C., or    -   ii) a content of 2,1 erythro regiodefects as determined from        ¹³C-NMR spectroscopy of ≤0.10 mol.-%, or    -   iii) an isotactic triad fraction (mm) determined from ¹³C-NMR        spectroscopy in the range from 95.0 to 98.0%, or    -   iv) a molecular weight distribution Mw/Mn measured according to        ISO 16014 in the range of ≥4.0, preferably in the range from 4.0        to 8.0, and most preferably in the range from 4.0 to 7.0, or    -   v) a xylene cold soluble fraction (XCS) determined at 23° C.        according ISO 16152 in the range from 1.5 to 3.5 wt.-%,        preferably in the range from 1.5 to 3.0 wt.-%.

Alternatively, the polypropylene (PP2), preferably the polypropylenehomopolymer (H-PP2), has

-   -   i) a melting temperature Tm measured by differential scanning        calorimetry (DSC) in the range from 162 to 170° C., preferably        in the range from 162 to 168° C., and    -   ii) a content of 2,1 erythro regiodefects as determined from        ¹³C-NMR spectroscopy of ≤0.10 mol.-%, and    -   iii) an isotactic triad fraction (mm) determined from ¹³C-NMR        spectroscopy in the range from 95.0 to 98.0%, and    -   iv) a molecular weight distribution Mw/Mn measured according to        ISO 16014 in the range of ≥4.0, preferably in the range from 4.0        to 8.0, and most preferably in the range from 4.0 to 7.0, and    -   v) a xylene cold soluble fraction (XCS) determined at 23° C.        according ISO 16152 in the range from 1.5 to 3.5 wt.-%,        preferably in the range from 1.5 to 3.0 wt.-%.

The polypropylene (PP2), preferably the polypropylene homopolymer(H-PP2), is preferably produced by a single- or multistage processpolymerization of propylene such as bulk polymerization, gas phasepolymerization, slurry polymerization, solution polymerization orcombinations thereof. The polypropylene (PP2), preferably thepolypropylene homopolymer (H-PP2), can be made either in loop reactorsor in a combination of loop and gas phase reactor. Those processes arewell known to one skilled in the art.

In order to overcome the drawbacks of the prior art, it is appreciatedthat the polypropylene (PP2), preferably the polypropylene homopolymer(H-PP2), is preferably polymerized in the presence of a Ziegler-Nattacatalyst, which are known to those skilled in the art.

The Filler (F)

In addition, the polypropylene composition according to the presentinvention may comprises a filler (F) in amounts from 0 to 30.0 wt.-%,based on the total weight of the polypropylene composition.

Preferably, the polypropylene composition comprises the filler (F) inamounts from 2 to 20 wt.-%, like in the range of 3 to 15 wt.-%, based onthe total weight of the polypropylene composition.

In one specific embodiment, the polypropylene composition is free of afiller (F).

Preferably, the filler (F) is a mineral filler (F).

If present, the filler (F) is preferably selected from talcum, mica,wollastonite, glass fibers, carbon fibers and mixtures thereof.

In general, the filler (F) may have a particle size d₅₀ in the rangefrom 5 to 30 μm, preferably in the range from 5 to 25 μm, morepreferably in the range from 5 to 20 μm.

A preferred filler (F) is talc. Preferably talc having a particle sized₅₀ in the range from 0.1 to 10 μm, preferably in the range from 0.2 to6.0 μm, more preferably in the range from 0.3 to 4.0 μm is used asfiller (F). Most preferably talc is used as the sole filler (F). Stillmore preferably the talc used has a top-cut particle size (95% ofparticles below that size, according to ISO 787-7) of 0.8 to 50 μm,preferably from 1.0 to 25 μm and most preferably from 1.2 to 20 μm.

The at Least One Additive

It is required that the polypropylene composition comprises at least oneadditive in an amount ranging from 2.5 to 5 wt.-%, based on the totalweight of the composition. The at least one additive is selected fromthe group consisting of colorants, pigments such as carbon black,stabilisers, acid scavengers, nucleating agents, foaming agents,antioxidants and mixtures thereof.

It is to be noted that the term “at least one” additive in the meaningof the present invention means that the additive comprises one or moreadditives(s). In one embodiment, the additive is thus one additive.Alternatively, the additive comprises two or more, such as two or three,additives.

Preferably, the additive comprises two or more, such as two or three,additives.

The term “additive” covers also additives which are provided as amasterbatch containing the polymeric carrier material as discussedabove.

It is appreciated that the polypropylene composition preferablycomprises a nucleating agent. Thus, it is preferred that thepolypropylene composition comprises a nucleating agent and one or morefurther additives selected from colorants, pigments such as carbonblack, stabilisers, acid scavengers, foaming agents, antioxidants andmixtures thereof.

For example, the polypropylene composition contains preferably anucleating agent, more preferably an α-nucleating agent. Even morepreferred the polypropylene composition according to the presentinvention is free of β-nucleating agents. Accordingly, the nucleatingagent is preferably selected from the group consisting of

-   (i) salts of monocarboxylic acids and polycarboxylic acids, e.g.    sodium benzoate or aluminum tert-butylbenzoate, and-   (ii) dibenzylidenesorbitol (e.g. 1,3:2,4 dibenzylidenesorbitol) and    C₁-C₈-alkyl-substituted dibenzylidenesorbitol derivatives, such as    methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or    dimethyldibenzylidenesorbitol (e.g. 1,3:2,4 di(methylbenzylidene)    sorbitol), or substituted nonitol-derivatives, such as    1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol,    and-   (iii) salts of diesters of phosphoric acid, e.g. sodium    2,2′-methylenebis (4, 6-di-tert-butylphenyl) phosphate or    aluminium-hydroxy-bis[2,2′-methylene-bis(4,6-di-t-butylphenyl)phosphate],    and-   (iv) vinylcycloalkane polymer and vinylalkane polymer, and-   (v) mixtures thereof.

Preferably, the α-nucleating agent is a nucleating agent containing1,2-cyclohexane dicarboxylic acid. For example, commercially availableα-nucleating agents, which can be used for the composition of theinvention are, for example, Irgaclear XT 386(N-[3,5-bis-(2,2-dimethyl-propionylamino)-phenyl]-2,2-dimethylpropionamide)from Ciba Speciality Chemicals, Hyperform HPN-68L and Hyperform HPN-20Efrom Milliken & Company.

In one embodiment, the polypropylene composition comprises from 0.1 to0.5 wt.-%, based on the total weight of the composition, of thenucleating agent. Preferably, the polypropylene composition comprisesfrom 0.1 to 0.5 wt.-%, based on the total weight of the composition, ofa nucleating agent containing 1,2-cyclohexane dicarboxylic acid.

Additionally or alternatively, the polypropylene composition comprises(a) foaming agent(s).

Throughout the present invention, the term “foaming agent” refers to anagent which is capable of producing a cellular structure in apolypropylene composition during foaming. Suitable foaming agentscomprise e.g. bicarbonates, preferably bicarbonates and polyolefincarrier. Such foaming agents are commercially available, from e.g. EIWACHEMICAL IND. CO., LTD.

The polypropylene composition of the present invention comprises thefoaming agent preferably in an amount of less than 10 wt.-%, morepreferably from 1 wt.-% to 7 wt.-% and most preferably from 1.5 wt.-% to3 wt.-%, based on the total weight of the polypropylene composition.

Generally, such additives are commercially available and are described,for example, in “Plastic Additives Handbook”, 5th edition, 2001 of HansZweifel.

In one preferred embodiment, the polypropylene composition comprises (a)nucleating agent(s) and (a) foaming agent(s) and optionally at least oneadditive selected from colorants, pigments such as carbon black,stabilisers, acid scavengers, antioxidants and mixtures thereof.

Preferably, the polypropylene composition comprises (a) nucleatingagent(s) and (a) foaming agent(s) and at least one additive selectedfrom colorants, pigments such as carbon black, stabilisers, acidscavengers, antioxidants and mixtures thereof.

Articles and Uses

The present polypropylene composition can be used for the production ofarticles such as molded articles, preferably injection molded articles.Furthermore, the present polypropylene composition can be used for theproduction of foamed articles such as foamed injection molded articles.Even more preferred is the use for the production of automotivearticles, especially of automotive interior articles and exteriorarticles, like instrumental carriers, front end module, shrouds,structural carriers, bumpers, side trims, step assists, body panels,spoilers, dashboards, interior trims and the like. Preferably, thearticle is an automotive interior article.

The present invention thus refers in another aspect to an injectionmolded article as well as a foamed article, preferably foamed injectionmolded article, comprising the polypropylene composition as definedherein.

As already described above, the polypropylene homopolymer (H-PP1), asdefined herein, advantageously reduces the stiffness reduction factor ofa foamed injection molded article.

Thus, the present invention refers in another aspect to the use of apolypropylene homopolymer (H-PP1) for reducing the stiffness reductionfactor of a foamed injection molded article by at least 40 as determinedby the difference of the flexural modulus measured according to ISO 178of the non-foamed and foamed injection molded article and compared to anarticle comprising the same amount of a polypropylene which has beenpolymerized in the presence of a Ziegler-Natta catalyst, wherein thepolypropylene homopolymer (H-PP1) has

-   -   i) a melting temperature Tm measured by differential scanning        calorimetry (DSC) in the rage from 150 to 160° C.,    -   ii) a content of 2,1 erythro regiodefects as determined from        ¹³C-NMR spectroscopy in the range from 0.50 to 1.00 mol.-%,    -   iii) an isotactic triad fraction (mm) determined from ¹³C-NMR        spectroscopy of at least 97.5%, and    -   iv) a xylene cold soluble fraction (XCS) determined at 23° C.        according ISO 16152 of equal or below 1.5 wt.-%

With regard to the polypropylene homopolymer (H-PP1) and preferredembodiments thereof, it is referred to the statements provided abovewhen discussing the polypropylene homopolymer (H-PP1) present in thepolypropylene composition in more detail.

The present invention will now be described in further detail by theexamples provided below.

EXAMPLES 1. Definitions/Measuring Methods

The following definitions of terms and determination methods apply forthe above general description of the invention as well as to the belowexamples unless otherwise defined.

MFR₂ (230° C.) was measured according to ISO 1133 (230° C., 2.16 kgload).

The xylene cold solubles (XCS, wt.-%) were determined at 25° C.according to ISO 16152; first edition; 2005-07-01.

Intrinsic viscosity is measured according to DIN ISO 1628/1, October1999 (in Decalin at 135° C.).

Quantification of Microstructure by NMR Spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used toquantify the comonomer content of the polymers. Quantitative ¹³C {¹H}NMR spectra were recorded in the solution-state using a Bruker AdvanceIII 400 NMR spectrometer operating at 400.15 and 100.62 MHz for ¹H and¹³C respectively. All spectra were recorded using a ¹³C optimised 10 mmextended temperature probehead at 125° C. using nitrogen gas for allpneumatics. Approximately 200 mg of material was dissolved in 3 ml of1,2-tetrachloroethane-d₂ (TCE-d₂) along withchromium-(III)-acetylacetonate (Cr(acac)₃) resulting in a 65 mM solutionof relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V.,Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution,after initial sample preparation in a heat block, the NMR tube wasfurther heated in a rotatary oven for at least 1 hour. Upon insertioninto the magnet the tube was spun at 10 Hz. This setup was chosenprimarily for the high resolution and quantitatively needed for accurateethylene content quantification. Standard single-pulse excitation wasemployed without NOE, using an optimised tip angle, 1 s recycle delayand a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu,X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag.Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R.,Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007,28, 1128). A total of 6144 (6 k) transients were acquired per spectra.

Quantitative ¹³C {¹H} NMR spectra were processed, integrated andrelevant quantitative properties determined from the integrals usingproprietary computer programs. All chemical shifts were indirectlyreferenced to the central methylene group of the ethylene block (EEE) at30.00 ppm using the chemical shift of the solvent. This approach allowedcomparable referencing even when this structural unit was not present.Characteristic signals corresponding to the incorporation of ethylenewere observed Cheng, H. N., Macromolecules 17 (1984), 1950).

With characteristic signals corresponding to 2,1 erythro regio defectsobserved (as described in L. Resconi, L. Cavallo, A. Fait, F.Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N.,Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu,Macromolecules 2000, 33 1157) the correction for the influence of theregio defects on determined properties was required. Characteristicsignals corresponding to other types of regio defects were not observed.

The comonomer fraction was quantified using the method of Wang et. al.(Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157) throughintegration of multiple signals across the whole spectral region in the¹³C {¹H} spectra. This method was chosen for its robust nature andability to account for the presence of regio-defects when needed.Integral regions were slightly adjusted to increase applicability acrossthe whole range of encountered comonomer contents.

For systems where only isolated ethylene in PPEPP sequences was observedthe method of Wang et. al. was modified to reduce the influence ofnon-zero integrals of sites that are known to not be present. Thisapproach reduced the overestimation of ethylene content for such systemsand was achieved by reduction of the number of sites used to determinethe absolute ethylene content to:E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

Through the use of this set of sites the corresponding integral equationbecomes:E=0.5(I _(H) +I _(G)+0.5(I _(C) +I _(D)))

using the same notation used in the article of Wang et. al. (Wang, W-J.,Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolutepropylene content were not modified.

The mole percent comonomer incorporation was calculated from the molefraction:E [mol %]=100*fE

The weight percent comonomer incorporation was calculated from the molefraction:E [wt %]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

The comonomer sequence distribution at the triad level was determinedusing the analysis method of Kakugo et al. (Kakugo, M., Naito, Y.,Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This methodwas chosen for its robust nature and integration regions slightlyadjusted to increase applicability to a wider range of comonomercontents.

Flexural Modulus was determined in 3-point-bending according to ISO 178on injection molded specimens of 80×10×4 mm prepared in accordance withISO 294-1:1996.

DSC analysis, melting temperature (T_(m)), crystallization temperature(T_(c)), heat of fusion (H_(m)) and heat of crystallization (H_(c)):measured with a TA Instrument Q2000 differential scanning calorimetry(DSC) on 5 to 7 mg samples. DSC is running according to ISO 11357/part3/method C2 in a heat/cool/heat cycle with a scan rate of 10° C./min inthe temperature range of −30 to +225° C. Crystallization temperature(T_(c)) and heat of crystallization (H_(c)) are determined from thecooling step, while melting temperature (T_(m)) and heat of fusion(H_(m)) are determined from the second heating step.

Glass transition temperature Tg and storage modulus G′ were determinedby dynamic mechanical analysis (DMTA) according to ISO 6721-7. Themeasurements were done in torsion mode on compression moulded samples(40×10×1 mm3) between −100° C. and +150° C. with a heating rate of 2°C./min and a frequency of 1 Hz. While the Tg was determined from thecurve of the loss angle (tan(δ)), the storage modulus (G′) curve wasused to determine the temperature for a G′ of 40 MPa representing ameasure for the heat deflection resistance.

Puncture energy and Energy to max Force were determined on plaques withdimensions 148×148×2 mm during instrumented falling weight impacttesting according to ISO 6603-2. The test was performed at roomtemperature with a lubricated tup with a diameter of 20 mm and impactvelocity of 10 mm/s.

Number average molecular weight (M_(n)) and weight average molecularweight (M_(w)) were determined by Gel Permeation Chromatography (GPC)according to ISO 16014-4:2003 and ASTM D 6474-99. A PolymerChar GPCinstrument, equipped with infrared (IR) detector was used with 3× Olexisand 1× Olexis Guard columns from Polymer Laboratories and1,2,4-trichlorobenzene (TCB, stabilized with 250 mg/L 2,6-Di tertbutyl-4-methyl-phenol) as solvent at 160° C. and at a constant flow rateof 1 mL/min. 200 μL of sample solution were injected per analysis. Thecolumn set was calibrated using universal calibration (according to ISO16014-2:2003) with at least 15 narrow MWD polystyrene (PS) standards inthe range of 0.5 kg/mol to 11 500 kg/mol. Mark Houwink constants for PS,PE and PP used are as described per ASTM D 6474-99. All samples wereprepared by dissolving 5.0-9.0 mg of polymer in 8 mL (at 160° C.) ofstabilized TCB (same as mobile phase) for 2.5 hours for PP or 3 hoursfor PE at max. 160° C. under continuous gentle shaking in theautosampler of the GPC instrument.

Particle size d₅₀ and top cut d₉₅ were calculated from the particle sizedistribution [mass percent] as determined by gravitational liquidsedimentation according to ISO 13317-3 (Sedigraph).

Cell structure of the foamed parts was determined by light microscopyfrom a cross-section of the foamed injection-molded plate.

Total carbon emission was determined according to VDA 277:1995 frompellets.

Volatile organic content (VOC) is measured according to VDA 278, October2011.

2. Examples

Synthesis of Metallocene:

The metallocene(rac-anti-dimethylsilandiyl(2-methyl-4-phenyl-5-methoxy-6-tert-butylindenyl)(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconiumdichloride) has been synthesized as described in WO 2013/007650. Themetallocene containing catalyst was prepared using said metallocene anda catalyst system of MAO and trityl tetrakis(pentafluorophenyl)borateaccording to Catalyst 3 of WO2015/11135 with the proviso that thesurfactant is2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-1-propanol.

TABLE 1 Polymerization process conditions and properties of thepolypropylene homopolymer H-PP1 B1 Prepoly reactor Temp. (° C.) 20Press. (kPa) 5238 B2 loop reactor Temp. (° C.) 70 Press. (kPa) 5292H2/C3 ratio (mol/kmol) 0.42 Polymer Split (wt.-%) 49.0 MFR2 (g/10 min)91.0 XCS (%) 1.4 B3 GPR Temp. (° C.) 80 Press. (kPa) 2406 H2/C3 ratio(mol/kmol) 3.2 Polymer Split (wt.-%) 51.0 MFR2 (g/10 min) 71.0 XCS (%)1.3

The polypropylene compositions were prepared by mixing in a co-rotatingtwin-screw extruder ZSK18 from Coperion with a typical screwconfiguration and a melt temperature in the range of 200-220° C. Themelt strands were solidified in a water bath followed by strandpelletization.

TABLE 2 Overview of the composition for inventive and comparativeexamples IE1, IE2 and CE1 IE1 IE2 CE1 H-PP1 [wt.-%] 96.5 47.5 PP2[wt.-%] 49 96.5 Additives [wt.-%] 3.5 3.5 3.5 H-PP1 is an isotacticunimodal polypropylene homopolymer of Borealis AG having a melt flowrate MFR₂ (230° C.) of about 71 g/10 min, prepared in the presence of asingle-site catalyst as outlined in table 1. PP2 is the commercialunimodal polypropylene homopolymer HJ120UB of Borealis AG having a meltflow rate MFR₂ (230° C.) of about 75 g/10 min, a Tm of 164° C., adensity of 0.905 g/cm³, and is prepared in the presence of aZiegler-Natta catalyst. Additives includes 1.5 wt.-% carbon black, 0.2wt.-% of the nucleating agent Hyperform HPN-20E from Milliken & Company,0.15 wt.-% of the antioxidant Irganox B215FF of BASF AG, Germany, 0.15wt.-% calcium stearate, and 1.5 wt.-% of a carrier material.

The mechanical characteristics of the inventive examples IE1 and 1E2 andof comparative example CE1 are indicated in table 3 below.

TABLE 3 Characteristics of the prepared polypropylene (PP) compositionsIE1 IE2 CE1 Properties from pellets MFR₂ [g/10 min]  70.4   67.6   75.3Total carbon emissions μgC/g 4  21  40 VOC/FOG μg/g 17/79 98/317 170/506Tm [° C.] 156  161 165 Tc [° C.] 123  127 129 Tg [° C.]   2.0  0  −2 G′[MPa] 1030   910 1210  Non-foamed injection molded plates, 2 mm Flexuralmodulus [MPa] 1792 ± 16  1879 ± 25  1958 ± 20  Puncture energy, 23° C.[J] 3    0.35    0.8 Energy to max. force [J] 2.73 ± 1.35 1.28 ± 0.370.58 ± 0.39 VOC [μg/g] 4  74 170 Foamed injection molded plates, coreback, 3 mm Flexural modulus [MPa] 1107 ± 40  1153 ± 18  1191 ± 33 Puncture energy, 23° C. [J] 2  1  2 Energy to max. force [J] 0.64 ± 0.2 0.43 ± 0.09 0.43 ± 0.01 Cell size [μm] 77 ± 19 99 ± 22 105 ± 22  VOC[μg/g] 22  160 276 Stiffness reduction factor (flexural 685  726 767modulus non-foamed - flexural modulus foamed)

From table 3, it can be gathered that foamed plates of IE1 have finecells and lower stiffness reduction factor defined by the difference instiffness of compact non-foamed and foamed part in comparison to thecomparative example CE1. At similar melt flow rate (MFR) IE1 has alsolower VOC/FOG then CE1 mainly due to the nature of the catalyst used toproduce the polymer. IE1 can be used also as modifier for CE1. Additionof IE1 to CE1 (i.e. IE2) results in a lower stiffness reduction factor,improved emissions and finer cells.

The invention claimed is:
 1. A polypropylene composition comprising: a)from 45 to 97.5 wt. %, based on the total weight of the composition, ofa polypropylene homopolymer (H-PP1) having; i) a melting temperature Tmmeasured by differential scanning calorimetry (DSC) in the range from150 to 160° C., ii) a content of 2,1 erythro regiodefects as determinedfrom ¹³C-NMR spectroscopy in the range from 0.50 to 1.00 mol. %, iii) anisotactic triad fraction (mm) determined from ¹³C-NMR spectroscopy of atleast 97.5%, and iv) a xylene cold soluble fraction (XCS) determined at23° C. according ISO 16152 of equal or below 1.5 wt. %, b) from 0 to 55wt. %, based on the total weight of the composition, of a polypropylene(PP2), c) from 0 to 30 wt. %, based on the total weight of thecomposition, of a filler (F), and d) from 2.5 to 5 wt. %, based on thetotal weight of the composition, of at least one additive selected fromthe group consisting of colorants, pigments, carbon black, stabilisers,acid scavengers, nucleating agents, foaming agents, antioxidants andmixtures thereof, wherein the sum of the amount of the polypropylenehomopolymer (H-PP1), the polypropylene (PP2), the filler (F) and the atleast one additive in the polypropylene composition is 100.0 wt. %. 2.The polypropylene composition according to claim 1, wherein thecomposition comprises: a) from 95 to 97.5 wt. %, based on the totalweight of the composition, of the polypropylene homopolymer (H-PP1), andb) from 2.5 to 5 wt. %, based on the total weight of the composition, ofat least one additive selected from the group consisting of colorants,pigments, carbon black, stabilisers, acid scavengers, nucleating agents,foaming agents and mixtures thereof.
 3. The polypropylene compositionaccording to claim 1, wherein the composition comprises: a) from 45 to52.5 wt. %, based on the total weight of the composition, of thepolypropylene homopolymer (H-PP1), b) from 45 to 55 wt. %, based on thetotal weight of the composition, of a polypropylene (PP2), and c) from2.5 to 5 wt. %, based on the total weight of the composition, of atleast one additive selected from the group consisting of colorants,pigments, carbon black, stabilisers, acid scavengers, nucleating agents,foaming agents and mixtures thereof.
 4. The polypropylene compositionaccording to claim 1, wherein the composition has: a) a melt flow rateMFR₂ (230° C.) measured according to ISO 1133 in the range of 15.0 to80.0 g/10 min; and/or b) a content of volatile organic compounds nogreater than 170 μg/g composition in non-foamed injection moulded parts;and/or c) a content of volatile organic compounds no greater than 200μg/g composition in pellet form; and/or d) a glass transitiontemperature Tg (measured with DMTA according to ISO 6721-7) of 0° C. orabove.
 5. The polypropylene composition according to claim 1, whereinthe polypropylene (PP2) is a polypropylene homopolymer (H-PP2).
 6. Thepolypropylene composition according to claim 1, wherein thepolypropylene homopolymer (H-PP1) and/or the polypropylene (PP2)has/have a melt flow rate MFR₂ (230° C.) measured according to ISO 1133in the range of 15.0 to 100.0 g/10 min.
 7. The polypropylene compositionaccording to claim 1, wherein the melt flow rate MFR₂ (230° C.) measuredaccording to ISO 1133 of the polypropylene homopolymer (H-PP1) differsfrom the melt flow rate MFR₂ (230° C.) measured according to ISO 1133 ofthe polypropylene (PP2) by less than 20.0 g/10 min.
 8. The polypropylenecomposition according to claim 1, wherein the polypropylene homopolymer(H-PP1): i) is unimodal, and/or ii) has a molecular weight distributionMw/Mn measured according to ISO 16014 in the range of ≤4.0.
 9. Thepolypropylene composition according to claim 1, wherein thepolypropylene (PP2) has: i) a melting temperature Tm measured bydifferential scanning calorimetry (DSC) in the range from 162 to 170°C., and/or ii) a content of 2,1 erythro regiodefects as determined from¹³C-NMR spectroscopy of ≤0.10 mol. %, and/or iii) an isotactic triadfraction (mm) determined from ¹³C-NMR spectroscopy in the range from95.0 to 98.0%, and/or iv) a molecular weight distribution Mw/Mn measuredaccording to ISO 16014 in the range of ≥4.0, and/or v) a xylene coldsoluble fraction (XCS) determined at 23° C. according ISO 16152 in therange from 1.5 to 3.5 wt. %.
 10. The polypropylene composition accordingto claim 1, wherein the composition has a bimodal molecular structure.11. The polypropylene composition according to claim 1, wherein thefiller (F) is selected from talcum, mica, wollastonite, glass fibers,carbon fibers and mixtures thereof.
 12. An injection molded articlecomprising the polypropylene composition according to claim
 1. 13. Afoamed article, comprising the polypropylene composition according toclaim 1.